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Environmental temperature fundamentally shapes insect physiology, fitness and interactions with parasites. Differential climate warming effects on host versus parasite biology could exacerbate or inhibit parasite transmission, with far-reaching implications for pollination services, biocontrol and human health. Here, we experimentally test how controlled temperatures influence multiple components of host and parasite fitness in monarch butterflies (Danaus plexippus) and their protozoan parasitesOphryocystis elektroscirrha. Using five constant-temperature treatments spanning 18–34°C, we measured monarch development, survival, size, immune function and parasite infection status and intensity. Monarch size and survival declined sharply at the hottest temperature (34°C), as did infection probability, suggesting that extreme heat decreases both host and parasite performance. The lack of infection at 34°C was not due to greater host immunity or faster host development but could instead reflect the thermal limits of parasite invasion and within-host replication. In the context of ongoing climate change, temperature increases above current thermal maxima could reduce the fitness of both monarchs and their parasites, with lower infection rates potentially balancing negative impacts of extreme heat on future monarch abundance and distribution.
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Temperature and Resources Interact to Affect Transmission via Host Foraging Rate and Susceptibility
ABSTRACT Environmental conditions such as temperature and resource availability can shape disease transmission by altering contact rates and/or the probability of infection given contact. However, interactive effects of these factors on transmission processes remain poorly understood. We develop mechanistic models and fit them to experimental data to uncover how temperature and resources jointly affect transmission of fungal parasites (Metschnikowia bicuspidata) in zooplankton hosts (Daphnia dentifera). Model competition revealed interactive effects of temperature and resources on both contact rates (host foraging) and the probability of infection given contact (per‐parasite susceptibility). Foraging rates increased with temperature and decreased with resources (via type‐II functional response), but this resource effect weakened at warmer temperatures due to shorter handling times. Per‐parasite susceptibility increased with resources at cooler temperatures but remained consistently high when warmer. Our analysis demonstrates that temperature and resources interact to shape transmission processes and provides a general theoretical framework for other host–parasite systems.
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- Award ID(s):
- 2245422
- PAR ID:
- 10615895
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Ecology Letters
- Volume:
- 28
- Issue:
- 6
- ISSN:
- 1461-023X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/ele.70151
